178433024domain: NAppears in sequencesa(n) = 2^n*(2^n - 1)*(2^n - 2)/6.at n=10A026740Number of ways to choose three points in an (n X n)-grid (or geoplane).at n=31A178208a(n) is the smallest tetrahedral number with exactly n prime factors (counted with multiplicity), or -1 if no such number exists.at n=14A358927